Two British soldiers were killed in Afghanistan yesterday while taking part in the current offensive against militant strongholds in the southern province of Helmand.

The soldiers, from 1st Battalion Coldstream Guards and 1st Battalion Scots Guards, were killed in an explosion and a firefight respectively while taking part in operation Moshtarak. Their families have been informed. Britain has lost 263 soldiers in Afghanistan since operations began in 2001.

The Taliban resistance to the operation has been sporadic but fierce at times. The main danger is from improvised explosive devices (IEDs), which are planted by the Taliban across the area of Marjah and Nad Ali, the insurgent strongholds targeted by the offensive.

The Taliban were given weeks of advanced notice of the operation, allowing them to lay down extensive IED defences. Coalition commanders are concerned that only a small proportion of these bombs have been discovered. Separately, seven Afghan police officers were killed in the northern province of Kunduz, from a misdirected Nato airstrike. They were killed in the district of Imam Sahib in Kunduz, close to the border with Tajikistan. The officers had been ambushed by Taliban.

"Nato attacked from the air in error. They hit a police vehicle, which killed seven and injured two more police officers," said Zemari Bashari, spokesman for Afghanistan's interior ministry.

Because of such tragedies, Nato has moved to limit the use of and tighten rules governing such strikes.